/* * Interrupt handling in Real-Time. Play sounds with PC speaker. * * (C) Michael Barabanov, 1997 *  (C) FSMLabs  1999. baraban@fsmlabs.com *  Released under the GNU GENERAL PUBLIC LICENSE Version 2, June 1991 *  Any use of this code must include this notice. * */#include <linux/mc146818rtc.h>#include <pthread.h>#include <rtl_fifo.h>#include <rtl_core.h>#include <rtl_time.h>#include <rtl.h>#define FIFO_NO 3static int filter(int x){	static int oldx;	int ret;	if (x & 0x80) {		x = 382 - x;	}	ret = x > oldx;	oldx = x;	return ret;	}pthread_t thread;void *sound_thread(void *param){	char data;	char temp;	rtl_stop_interrupts();	while (1) {		pthread_suspend_np(pthread_self());		if (rtf_get(FIFO_NO, &data, 1) > 0) {			data = filter(data);	/* 		if (data) conpr("1"); else conpr("0"); */			temp = inb(0x61);            			temp &= 0xfc;			if (data) {				temp |= 3;			}			outb(temp,0x61);		}	}}unsigned int intr_handler(unsigned int irq, struct pt_regs *regs) {	pthread_wakeup_np (thread); 	(void) CMOS_READ(RTC_REG_C);        /* clear IRQ */ 	rtl_hard_enable_irq (8);	return 0;}char save_cmos_A;char save_cmos_B;int init_module(void){	char ctemp;	pthread_create (&thread,  NULL, sound_thread, NULL);	if (!I8253_channel2_free()) {		conpr("RTLinux sound: can't use channel 2; bailing out\n");		return -1;	}	rtf_create(FIFO_NO, 4000);	/* this is just to ensure that the output of the counter is 1 */	outb_p(0xb0, 0x43);	/* binary, mode 0, LSB/MSB, ch 2 */	outb_p(0x1, 0x42);	outb_p(0x0, 0x42);	rtl_request_irq (8, intr_handler);	/* program the RTC to interrupt at 8192 Hz */	save_cmos_A = CMOS_READ(RTC_REG_A);	save_cmos_B = CMOS_READ(RTC_REG_B);	CMOS_WRITE(0x23, RTC_REG_A);  	/* 32kHz Time Base, 8192 Hz interrupt frequency */	ctemp = CMOS_READ(RTC_REG_B);	ctemp &= 0x8f;                	/* Clear */	ctemp |= 0x40;                	/* Periodic interrupt enable */	CMOS_WRITE(ctemp, RTC_REG_B); 	rtl_hard_enable_irq (8);	(void) CMOS_READ(RTC_REG_C);	return 0;} void cleanup_module(void){	rtf_destroy(FIFO_NO);	outb_p(0xb6, 0x43);	/* restore the original mode */	CMOS_WRITE(save_cmos_A, RTC_REG_A);	CMOS_WRITE(save_cmos_B, RTC_REG_B);	rtl_free_irq(8);	pthread_cancel (thread);	pthread_join (thread, NULL);}